Active Noise Control (ANC) systems attenuate undesired noise using feedforward and feedback structures, to adaptively remove undesired noise within a listening environment, such as within a vehicle cabin. In a vehicle cabin listening environment, potential sources of undesired noise come from the interaction between the vehicle's tires and a road surface on which the vehicle is traveling. A Road Noise Cancellation (RNC) system is a specific ANC system implemented on a vehicle in order to minimize undesirable road noise inside the vehicle cabin. RNC systems use vibration sensors to sense road induced vibrations generated from the tire and road interface that leads to unwanted road noise. This unwanted road noise inside the cabin is then cancelled, or reduced in level, by using speakers to generate sound waves that are ideally opposite in phase and identical in magnitude to the noise to be reduced at one or more listeners ears. RNC systems are adaptive Least Mean Square (LMS) systems that continuously adapt W filters based on both acceleration inputs from the sensors located in various positions around a vehicle's suspension system and on signals of microphones located in various positions inside the vehicle's cabin.
When a vehicle is under operation, for example driving along a first road surface (i.e., paved), and the road surface changes to a second surface (i.e., gravel), the RNC system must adapt. It may take several minutes to achieve optimal road noise cancellation because the system starts adapting from its previous state, which had been continuously optimized for the first road surface. During the time it takes for the RNC system to converge to a new optimal state, the output of the road noise cancellation system may be suboptimal which may diminish a user's experience within the vehicle cabin listening environment. During the initial adaptation time, the level of in-cabin noise at locations of the listeners' ears will be higher than if the system were fully adapted.
There is a need for a Road Noise Cancellation system that utilizes road type identification from a set of predetermined tuning parameters to apply W-filters and other road type optimized parameters that produce optimal RNC for the particular road type identified.